feat(groups): audio and video calls in group chats; release v6.6.6

A group call is N-1 ordinary 1:1 calls, one to each other member, each riding
the pairwise session that member already has — a transport a human already
authenticated by comparing the safety code. No mixer, no SFU, no point at which
two people's media meets anywhere but on a device.

Call control is separate from call media, because the two reach different sets
of people. Who opened a call, who joined and who left travels as group frames
signed with the sender's group identity key, so it reaches members currently
reachable only through a relay — and a relaying member can drop one but cannot
write one. Media flows only where a direct link exists, so a member without one
shows as connecting rather than being omitted. Frames carry a per-sender
sequence checked before the action, so a captured leave cannot end a later call,
and simultaneous calls converge on the lower random call id.

One capture is shared across every leg rather than one getUserMedia per member,
and legs answer without prompting: the flag permitting that is set only locally,
only while this user is in the call, and cleared when they leave.

UI: a gallery that sizes itself from the space it has, a spotlight view, an
active-speaker indicator read from the waveform, and the call surface in the
same visual language as the 1:1 one.

Also in this commit, the v6.5.0 language-suggestion work that had not been
pushed yet; its notes are in the changelog. And two fixes: the safety-code input
asks for digits rather than text, and starting a new chat from inside a group no
longer creates it behind the group where it cannot be seen — which had made it
impossible to connect to anyone new, or to add anyone to a group, while a group
was open.

Claude-Session: https://claude.ai/code/session_01XSxAkET3hQTkYDQfbjCQwZ

locales/es.json

@@ -36,6 +36,9 @@
   },
   "ui": {
     "language.label": "Idioma",
+    "language.suggest.text": "Esta página también está disponible en español.",
+    "language.suggest.cta": "Leer en español",
+    "language.suggest.dismiss": "Cerrar",
     "community.title": "Construye el futuro de la privacidad",
     "community.description": "SecureBit crece gracias a su comunidad. Tus ideas y comentarios dan forma al futuro de la comunicación segura, desarrollada de forma abierta y con validación ASN.1 completa de extremo a extremo.",
     "community.github": "Repositorio en GitHub",
@@ -781,6 +784,28 @@
     "offline.disconnect": "Desconectar",
     "offline.learnMore": "Más información",
     "pwa.installApp": "Instalar la app",
-    "chat.onWeb": "Estás en la versión web"
+    "chat.onWeb": "Estás en la versión web",
+    "groupCall.startVoice": "Iniciar llamada de voz grupal",
+    "groupCall.startVideo": "Iniciar videollamada grupal",
+    "groupCall.join": "Unirse",
+    "groupCall.dismiss": "Ahora no",
+    "groupCall.leave": "Salir de la llamada",
+    "groupCall.you": "Tú",
+    "groupCall.connecting": "Conectando…",
+    "groupCall.waitingLink": "Esperando un enlace directo…",
+    "groupCall.legFailed": "No se pudo conectar",
+    "groupCall.startedVoice": "{name} inició una llamada de voz",
+    "groupCall.startedVideo": "{name} inició una videollamada",
+    "groupCall.inCall": "{count} en la llamada",
+    "groupCall.err.permission_denied": "La llamada no pudo iniciarse - el acceso al micrófono y a la cámara está bloqueado. Permítelo para este sitio e inténtalo de nuevo.",
+    "groupCall.err.device_not_found": "La llamada no pudo iniciarse - no se encontró ningún micrófono en este dispositivo.",
+    "groupCall.err.device_busy": "La llamada no pudo iniciarse - otra aplicación está usando tu micrófono. Ciérrala e inténtalo de nuevo.",
+    "groupCall.err.media_failed": "La llamada no pudo iniciarse - no se pudo abrir el micrófono.",
+    "groupCall.err.call_in_progress": "Ya hay una llamada en este grupo. Únete en lugar de iniciar otra.",
+    "groupCall.err.not_ready": "Confirma el código del grupo antes de llamar.",
+    "groupCall.speaking": "{name} está hablando",
+    "groupCall.pin": "Ver a {name} en grande",
+    "groupCall.unpin": "Volver a todos",
+    "groupCall.showEveryone": "Todos"
   }
 }